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Correcting CIFs

Ensuring the correct syntax of a CIF file is essential for the smooth and rapid processing of crystallographic data, and helps provide useful information to the scientific community.

The CCDC’s CIF deposition and validation service runs a series of syntax checks on data being uploaded to make certain the data can be read by our automated systems. It is important to note the syntax checks only establish that the data are able to be interpreted, this does not make any judgement on the data quality or the chemistry of the structure(s).

Should the deposition and validation service highlight issues that require attention, it is possible to fix errors by directly editing the file contents in the browser window. The warnings should provide useful information; the file contents are also colour coded to show common CIF items including data blocks, loops and data items. By saving and rechecking the file(s), syntax errors can be easily corrected as part of the deposition process.

If it is not possible to correct the CIF file as part of the deposition process we recommend the use of the CCDC’s enCIFer program for CIF checking and editing, available as a free download. EnCIFer includes an extended range of checks and tools for correcting CIFs.

A comprehensive check of the consistency and integrity of crystal structure determinations in CIF format is available through our web deposition service with the integration of the IUCr’s CheckCIF service.

The IUCr’s CIF dictionary provides an up to date list of CIF data names, including the expected data value (e.g. number, text, permitted range etc.). Should particular data items cause syntax errors it is possible to include the text as a comment, by preceding the text with a # symbol (the CIF deposition and validation service will highlight such comments in green text).

If you are unable to upload an error-free CIF file, or have data in other formats, please email the CCDC’s deposition team at deposit@ccdc.cam.ac.uk where we will endeavour to assist you.